Na to stale nioe je jednoznacna odpoved
Clang 3.4 offered faster performance of compiled C/C++ code in several areas but GCC 4.9 also brings some performance improvements of its own over the current stable release. Clang still certainly outperforms GCC when it comes to compile times, but aside from that the compiler performance competition is rather mixed depending upon the particular code-base, workload, and processor.
http://www.phoronix.com/scan.php?page=article&item=llvm34_gcc49_compilers&num=5
su tu vysledky., kde je gcc o 15-20% rychlejsie ale aj vysledkuy, kde je kod spompilovany Clang/LLVM o 78% rychlejsi
http://www.phoronix.com/scan.php?page=article&item=llvm34_gcc49_compilers&num=5
a
http://www.phoronix.com/scan.php?page=article&item=llvm34_gcc49_compilers&num=3